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Distinguishing between structural models of β′-sialons using a combined solid-state NMR, powder XRD, and computational approach

Distinguishing between structural models of β′-sialons using a combined solid-state NMR, powder XRD, and computational approach
Distinguishing between structural models of β′-sialons using a combined solid-state NMR, powder XRD, and computational approach
β′-Sialons (Si6–zAlzOzN8–z, where 0 ≤ z ≤ 4.2) are studied using a combination of 29Si and 27Al solid-state NMR, using magnetic fields of up to 20 T, powder X-ray diffraction, and density functional theory (DFT) calculations of both the structure and NMR parameters. Four different structural models have been proposed in the literature for the replacement of silicon and nitrogen by aluminum and oxygen within a β-Si3N4-structured lattice. Experimental data are presented for the variation with composition (z) of the unit cell parameters from diffraction and the local coordination units present suggested by NMR data. The experimental data are compared to the changes with composition in the DFT calculations of the structure and the NMR parameters according to the four models, allowing the models to be distinguished. It is shown that only one of these, the domain model, is fully consistent with all of the experimental data and is, therefore, a good structural model for β′-sialons. More speculatively, it is suggested that for the domain model, 27Al NMR data might provide a constraint on the thickness of its aluminum-rich layers.
1089-5639
9729-9736
Seymour, V.R.
13587906-718e-4005-b7d6-bc7d522b5594
Smith, M.E.
abd04fbf-5f56-459d-89ec-e51ab2598c09
Seymour, V.R.
13587906-718e-4005-b7d6-bc7d522b5594
Smith, M.E.
abd04fbf-5f56-459d-89ec-e51ab2598c09

Seymour, V.R. and Smith, M.E. (2019) Distinguishing between structural models of β′-sialons using a combined solid-state NMR, powder XRD, and computational approach. Journal of Physical Chemistry A, 123 (45), 9729-9736. (doi:10.1021/acs.jpca.9b06729).

Record type: Article

Abstract

β′-Sialons (Si6–zAlzOzN8–z, where 0 ≤ z ≤ 4.2) are studied using a combination of 29Si and 27Al solid-state NMR, using magnetic fields of up to 20 T, powder X-ray diffraction, and density functional theory (DFT) calculations of both the structure and NMR parameters. Four different structural models have been proposed in the literature for the replacement of silicon and nitrogen by aluminum and oxygen within a β-Si3N4-structured lattice. Experimental data are presented for the variation with composition (z) of the unit cell parameters from diffraction and the local coordination units present suggested by NMR data. The experimental data are compared to the changes with composition in the DFT calculations of the structure and the NMR parameters according to the four models, allowing the models to be distinguished. It is shown that only one of these, the domain model, is fully consistent with all of the experimental data and is, therefore, a good structural model for β′-sialons. More speculatively, it is suggested that for the domain model, 27Al NMR data might provide a constraint on the thickness of its aluminum-rich layers.

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SiAlON paper revision 2 - Accepted Manuscript
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Accepted/In Press date: 23 October 2019
e-pub ahead of print date: 23 October 2019
Published date: 14 November 2019

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Local EPrints ID: 440904
URI: http://eprints.soton.ac.uk/id/eprint/440904
ISSN: 1089-5639
PURE UUID: 50dab6ce-c6c0-47ab-ad0d-44f1ae66ef6a

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Date deposited: 22 May 2020 16:37
Last modified: 22 Oct 2020 04:01

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Contributors

Author: V.R. Seymour
Author: M.E. Smith

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